The current method of shaping honeycomb core includes placing the core on a series of horizontal support rods and sliding the combination into an oven. The core is heated to its forming temperature, i.e., the particular temperature at which the core becomes shapable. Once the core is properly heated, the support rods and core are removed from the oven and the rods are retracted laterally to either side. This causes the core to fall loosely onto a lower die. There, a worker correctly aligns the core relative to the die. Next, the heated core is pressed for a period of time between the lower die and an upper die that is shaped in the reverse-image of the lower die (i.e., male/female die pair). After pressing the hot core, the dies continue to hold the core until it cools to a set temperature. Once set, the dies recede, and the shaping process is complete.
There are a number of disadvantages associated with the current method. A first disadvantage involves the forming temperature. The core must be heated to a particular temperature in order to bring it to a malleable state. The time spent retracting the rods and placing the core on the lower die allows the core to cool. A transfer of the core heat to the lower die begins when the core is transferred to the lower die. These steps lower the initial core temperature and must be accounted for by increasing the oven temperature to compensate for the anticipated heat loss and by requiring the worker to accurately position the core on the lower die in a short period of time. Both are disadvantageous: increased heat requires more energy and less temperature precision, short placement time decreases accuracy. Even if the initial temperature of the core is correctly adjusted, the forming temperature is adversely affected because the lower die continues to absorb heat from the core. This reduces the amount of time available for pressing the core at required forming temperature.
A second disadvantage with the current method involves cooling time. After the core has been pressed at its proper forming temperature for the required amount of time, the core must be allowed to cool to a particular temperature while being held at its new shape. If the core is released prior to reaching this temperature, it will tend to return (i.e., spring back) toward its original shape. This cool down period is longer than desired when using the current method due to the slow rate of heat dissipation from the dies.
A third disadvantage of the current method is the requirement for a worker to accurately position the hot core on the lower die prior to pressing. Human aligning is often imprecise, and typically worsens in time critical activities.
Prior art attempts to solve the above disadvantages have been unsuccessful. U.S. Pat. No. 5,084,226 describes a method of shaping a sheet of thermoplastic material by placing the material on a flexible support and heating the material and the support in an oven. Tension is applied to the support to force it to remain substantially horizontal during heating. Once removed from the oven, tension on the support is relaxed. This allows the material and support to drop into a lower female former (i.e., a female die), where the weight of the material itself forces the material to adopt the shape of the female die. This method is inadequate for shaping honeycomb core, because the weight of honeycomb core is insufficient to force the core to permanently adopt the shape of a die. This method also fails to overcome the disadvantages of core heat transfer to the die and slow heat dissipation from the die during cooling.
Based on the foregoing, it will be appreciated that there is a need for a shaping method and apparatus that provides fast and accurate transfer of a heated honeycomb core to a shaping mechanism, minimizes the heat loss of the core during forming of the core, and maximizes the heat loss of the core during the cooling period. The present invention is directed to fulfilling this need.